1. Field of the Invention
This invention relates to a shock isolator for isolating a device from surrounding shock in general and, more specifically, to a shock isolator for maintaining the integrity of boresight of a viewer for a tank and the like after the tank has been subjected to a severe shock by isolation of the viewer from the sources of adjacent shock waves.
2. Brief Description of the Prior Art
The Commander's Independent Thermal Viewer (CITV) used in a tank is required to survive the ballistic shock resulting from a non-penetrating round striking the tank turret, such survival being defined as retention of boresight after the shock as well as meeting stringent line-of-sight (LOS) jitter requirements before and after the ballistic shock. This requires that the viewer return almost identically to its original position shortly after the shock and that the isolator have a memory whereby the original position and shape thereof can be rapidly restored.
State of the art design techniques and hardware can satisfy either the survival or the boresight retention requirements or the LOS jitter requirements for a thermal viewer, however the prior art has been incapable of satisfying all three requirements simultaneously with sufficient precision whereby the equipment continues to operate under the required survival, boresight retention and LOS jitter specifications.
In the past and with past requirements, the designs of forward looking infrared (FLIR) sights have been capable of meeting their stabilization requirements in their operational vibration environments and to survive the shock levels (handling, gunfire, etc.) encountered during their usage with state of the art technology. Typically, the structurally induced LOS jitter of a thermal viewer is reduced to acceptable levels by stiffening the FLIR structure, including its mounting structure, so that the vibration environment produces little structural flexure. Depending upon the shock, devices can be protected in one of two ways.
One approach is to stiffen the device structure enough to eliminate any amplification of the shock by the structure. This approach is not feasible for CITV because the high frequency content of the ballistic shock would severely damage the sight assembly.
Another approach to protect a device from shock is to isolate it with an elastomeric or wire rope structure possessing resonant frequencies lower than the resonant frequencies of the device itself. These types of isolators typically have resonant frequencies in the 15 to 30 Hz range. Large sways are associated with shock isolated devices, however such sways are not acceptable for devices requiring precise alignment. For optical devices that require precise alignment and boresight retention, this type of isolation is unacceptable. Typically, FLIR devices involved in targeting systems are not shock mounted for this reason. However, the specifications for stabilized electro optical sights, such as CITVs, are continually being made more stringent and have now reached the point wherein the prior art techniques are presently incapable of providing the required specifications.